As shown in FIGS. 1 and 2, during manufacture of an organic light emitting display substrate, a pixel defining layer 1 with an opening is firstly formed on a base substrate, the opening and the base substrate forming an accommodation groove, and then ink is inkjet printed into the accommodation groove, wherein the ink forms a film layer 2, such as a hole transport layer, a light emitting layer, and the like, of a light emitting unit after drying.
During the drying of the ink to form a film layer, since a solvent of the ink mostly evaporates from the peripheral region of a layer of the ink, the ink will flows from the central region of the layer of the ink to the peripheral region. The flowage will allow a solute of the ink to move towards the peripheral region and to eventually deposit therein, so as to form the film layer 2 as shown in FIG. 2. A thickness of a peripheral region of the film layer 2 is greater than that of a central region of the film layer 2. After formation of various film layers of the light emitting unit, the light emitting effect of the light emitting unit is shown in FIG. 3. That is, a central region of the light emitting unit will be a bright display region, and a peripheral region (i.e., an annular region between a rectangular dotted line and a rectangular solid line adjacent to the rectangular dotted line, as shown in FIG. 1 or 3) of the light emitting unit will be a dark display region, this light emitting effect being referred to as a “coffee ring effect.” Although FIG. 1 shows that, in the peripheral region of the film layer 2 which has a greater thickness, each of the peripheral portions at the upper and lower sides has a width d1 equal to a width d2 of each of the peripheral portions at the left and right sides, each of the dark regions formed at the upper and lower sides of the peripheral region as shown in FIG. 3 appears larger due to the fact that the upper and lower sides of the film layer 2 of the light emitting unit are shorter than the left and right sides thereof.